There is a heat exchanger including a vessel, a plurality of heat transfer tubes disposed in the vessel, and tube support plates for supporting the heat transfer tubes in the vessel. In the heat exchanger, heat is exchanged between a primary coolant water and a secondary coolant water in such a manner that the primary coolant water is caused to flow in the heat transfer tubes as well as the secondary coolant water is caused to flow in the vessel.
Here, a wrapper (peripheral edge support member) for supporting the peripheral edges of the tube support plates and stay rods (inner peripheral portion support members) for supporting the inner peripheral portions of the tube support plates are disposed in the vessel, and the tube support plates are fixed by these members in the vessel.
A support structure disclosed in, for example, Patent Document 1 described below is known as a support structure of the heat transfer tubes. In Patent Document 1, tube support plates having a plurality of tube holes are used as tube support plates, and heat transfer tubes are supported by the tube support plates through being inserted into the tube holes.
Here, the tube support plates secure a thickness larger than that necessary to support the heat transfer tubes so that they can withstand a load they receive from a secondary coolant water and the like flowing in a vessel as well as they secure a predetermined degree of area to the regions between the tube holes (in other words, the volume of the portions between the tube holes).
Each of the tube support plates has a plurality of projecting portions each projecting radially inwardly from the inner surface of the tube hole and having a contact surface for supporting the heat transfer tube in an inside end and forms a conical guide structure from the inner surface to the contact surface, and a taper portion is formed to at least one end of the projecting portion so that the heat transfer tube can be easily inserted into the tube hole. More specifically, in the tube support plate, the length of the projecting portion in the axial direction of the tube hole is shorter than the length of the tube hole even if it includes the length of the taper portion, and the inner surface of the tube hole located nearer to the open end side thereof than the projecting portion is formed to a shape parallel with the axial line (shape without taper).    [Patent Document 1] Japanese Examined Patent Application, Publication No. 6-63712 (claim 1 and FIG. 4)